Different proteoglycans produced by the same cell can vary greatly with respect to their IdoA content and distribution. For example, decorin and biglycan have been found to contain blocks of IdoA, whereas versican only has isolated IdoA. Other studies have suggested that the core protein regulates the activity of the DS epimerases. This was demonstrated by the generation of chimeric proteins of decorin, which has a high content of IdoA, and colony-stimulating factor, a part-time proteoglycan with a low content of IdoA. The chimeric decorin–colony-stimulating factor contained less IdoA than the unmodified decorin 29. This suggests that core proteins carry information that may direct the proteoglycan cores to compartments within the Golgi complex with different amounts of DS epimerase activity 30.
